Heenan U.S. Pat. No. 3,332,327 ('327), Balint U.S. Pat. No. 3,409,344 (344) and Suhr U.S. Pat. No. 3,984,175 (175) each disclose a reflective pavement marker having a shell-like housing of synthetic resin with a reflective portion of light transmitting material formed with retro-directive reflector elements of the cube corner type. The housing is filled with an epoxy resin to give the pavement marker impact strength. One of the problems associated with this type of pavement marker is that of maintaining a secure adhesive bond between the filler material and the inner surface of the housing. If the filler (sometimes referred to as "potting material") separates from the inner surface of the housing, the housing will be vulnerable to cracking under the impact forces of vehicle wheels. This problem was addressed in the Balint 344 patent with the formation of interlocking ribs 57 projecting at right angles from the inner surface of the housing. The same problem was also addressed in the Suhr 175 parent by the provision of a plurality of projections 22 on the inner surface of the housing.